20" rims, What's the correct tire size?

[Dakine]

Hi Guys,
I recently purchased some 20" 8.5" rims on the net.
Can someone please help me?
I now need to put tires on them, But I need to get the correct tire size
to order.
Also if someone has a better place than Tire Rack to order from please
do chime in.
Thanks in advance

[E55 KEV]

245/45/20 is probably the best overall fit. However, only 3 companies make that size currently:

Goodyear
Avon
Toyo

Tire Rack will probably be the lowest priced merchant.